Parabola plot not displayed correctly

3 visualizaciones (últimos 30 días)
Sparkle89
Sparkle89 el 18 de Jul. de 2019
Editada: Sparkle89 el 18 de Jul. de 2019
I am trying to have a quadratic fit to my data.
X = randi(100,[40, 1])
Y = (2* (X.^2)) +(3*X) +(5);
X2 = [ones(size(X)) X X.^2]
m3 = X2 \ Y;
y3 = X2*m3;
scatter(X,Y);
hold on
plot(X,y3)
ylabel('Y')
title('y= ax^2+bx+c', 'FontSize',18)
hold off;
untitled1.jpg
However, when I display the plot istead of a single parabolic fir I am getting multiple lines.
Please help. I experimented this while learning linear regression.

Respuesta aceptada

KSSV
KSSV el 18 de Jul. de 2019
You are suing the random numbers for demo.....you have to sort them before you use:
X = randi(100,[40, 1]) ;
X = sort(X) ;
Y = (2* (X.^2)) +(3*X) +(5);
X2 = [ones(size(X)) X X.^2]
m3 = X2 \ Y;
y3 = X2*m3;
scatter(X,Y);
hold on
plot(X,y3)
ylabel('Y')
title('y= ax^2+bx+c', 'FontSize',18)
hold off;
  1 comentario
Sparkle89
Sparkle89 el 18 de Jul. de 2019
Editada: Sparkle89 el 18 de Jul. de 2019
Thank you.It worked. Can you explain the need for sorting because I could fit a line without sorting?

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